A number of apparatuses for treating multifilament yarn with air jets were known in the past. In many of the apparatuses, the air entering is introduced into a chamber or bore at an angle to the travel of yarn in a path that intersects the axis of the bore and this air jet results in fluttering or oscillation of the yarn which effects an entanglement or interlacing of the filaments. In others, the air introduction into the chamber or bore is tangential so that the air column whirls around the chamber or bore and imparts twist to the yarn.
Examples of air jet apparatuses in which air is introduced tangentially are my earlier U.S. Pat. Nos. 3,653,196, Apr. 4, 1972; 3,700,391, Oct. 24, 1972; and 3,831,363, Aug. 27, 1974. In each of my three patents the whirling air stream causes the yarn which is introduced to spin in the form of one or more loops similar in appearance to a jumping rope. This introduces a large amount of torque which is relieved with an abrupt change in direction around a rod to produce extremely effective texturization. Very substantial overfeed of the yarn going into the texturizing chamber is required.
A typical example of an interlacing or entanglement air jet is disclosed in U.S. Pat. No. 3,824,776 to London. In this patent, one or more multifilament yarns are pretexturized and then passed through a bore of an air jet apparatus in a straight path which follows the axis of the bore. Air at relatively high pressure is introduced into the bore at an angle of 45.degree. - 75.degree. with the air flow in the bore being cocurrent with the yarn direction. The patent describes only the use of pretexturized yarn and produces non-uniform, intermittent entanglement with nodal points between portions which are fluffed out. The non-uniform entanglement apparently somewhat resembles tiny sausage links or beads.
Another patent belonging to the same group is the U.S. Pat. No. 2,942,402 to Palm. One of the critical features of the invention is that there is a significant amount of leakage of air back through the yarn guide even though this is filled to a considerable extent by yarn. In Palm the yarn is fed to the bore with substantial overfeed and moves through the bore along a path which follows the axis of the bore. The product produced by Palm is voluminous and contains loops of individual filaments which project from the main body of the yarn.
My co-pending U.S. application Ser. No. 607,129, filed Aug. 25, 1975 relates to an improved air entangling apparatus in the form of a block in which an air jet enters a central bore at substantially right angle thereto. The bore extends all the way through the block and preferably has a uniform cross section so that air leaves at both ends of the bore. The incoming air jet strikes the upper wall of the central bore at a point opposite to the point of air introduction and splits to form two vortices in the upper portion of the central bore. Yarn introduction into the central bore is upstream from the air jet and is at an angle so that the yarn moves to the top of the turbulent air stream in the area of formation of the air vortices, where it oscillates back and forth across the stream. The yarn moves for a short distance countercurrent to the air leaving the upstream end of the central bore and then cocurrent with the air stream leaving the other end of the bore. The angled introduction of the yarn and the countercurrent air flow urge the yarn toward the top of the bore and hold the yarn in the upper portion of the bore in the area of formation of the air vortices.